Meteorology 2

8/8/2019 Meteorology 2

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METEOROLOGYPrivate Pilot License


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REGULATIONS


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The atmosphere Heating process in the

atmosphere

Atmospheric pressure

The general circulation pattern

Pressure system

Wind

Local winds

Atmospheric stability

Temperature inversions

Clouds

Precipitation

Fog and Mist

Thunderstorms

Air masses and Fronts

Tropical Cyclones

Meteorological services

COURSE OUTLINE


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THE ATMOSPHERE

What is Atmosphere? is a mixture of gases, Nitrogen

and Oxygen

So, Meteorology is .

a study of atmosphere and its

various components and how

they interact.

Nitrogen 78.1%

Oxygen 20.9%

Argon 0.9%

Carbon dioxide, Methane,

Rare (inert) gases0.1%


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Vertical Division of the Atmosphere


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Troposphere

The troposphere is the first

layer above the surface and

contains half of the Earth's

atmosphere.W

eather occursin this layer.

From sea level to 20,000 feet

over the poles and up to

48,000 feet at the equator. At the top of troposphere is a

boundary known as

tropopause.

Jetstream and clear air

turbulence is located in this

region.


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Stratosphere

The atmospheric level

above the tropopause is

known as stratosphere.

It extends up to 160,000

feet.

Many jet aircrafts fly in the

stratosphere because it is

very stable. Also, the

ozone layer absorbs

harmful rays from the Sun.

At the top of stratosphere is

a boundary known as

stratopause.


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Mesosphere

Directly above the

stratosphere is the area

called mesosphere.

It extends up to the

mesopause boundary at

about 280,000 feet.

Meteors or rock fragments

burn up in the mesosphere.


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Thermosphere

After mesosphere, is

the another layer

called thermosphere.

The thermosphere is

a layer with auroras. It

is also where thespace shuttle orbits.


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Temperatures in the atmosphere


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Heating Processes in the Atmosphere

Radiation

Solar

Radiation

TerrestrialRadiation

Seasons Winter

Spring

Summer

Autumn


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This phenomenon is related to specific heat.

The ability of an object to heat up, cool

down or retain heat.


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Color of surface

Dark object tends to absorb more

of the suns rays resulting in more

heating.

Light objects reflects most of the suns

rays back to the atmosphere with very

little effect on the surface.


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Effect ofVariable Heating

It creates convection currents,

an important method of heat

transfer.

Hot air expanding becomeslighter and rises. This is an

example ofconvection.

Cool air from the sea moving

to replace the air that hasrisen. We call this as sea

breeze which is an example of

advection.


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Other factors affecting Variable

Heating Clouds

It diffuses solar radiation.

Wind

Its mixing effect affects

different air masses.

Coastal Proximity Temperature in areas near

coastline tend to be less

extreme.


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Atmospheric Pressure

Gas molecules in the atmosphereare constantly moving.

They exert a force on the object they

hit. This force is called atmospheric

pressure.

To measure such pressure, abarometeris used.


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ISA Temperature:

15rC at MSL, decreasing at

2rC/ 1000 feet

Effect of Altitude on Atmospheric

Pressure ISA Pressure:

1013.25hPa, decreasing at

1hPa/ 30 feet


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If air is thin, more speed is required to obtain enoughlift for takeoff, therefore takeoff roll is longer.

At higher altitudes, due to the decreased density of

air, aircraft engines and propellers are less efficient.

Aircraft Performance


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Atmospheric Circulation

Atmospheric circulation is the movement of air around the surfaceof the earth.

The Earth is curve, tilted, rotating and orbiting around the sunthus affecting the amount of heat striking the surface.

In theory, areas of low pressure exist over the equatorial regions

while high pressure exist over the polar regions.


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Solar heating causes air to become less

dense and rise in the equatorial region.

As the warm air flows towards the poles, it

cools, becoming more dense, and sinks

back to the surface. This movement isknown as Subsidence.

The circulation of air is modified by several

factors one of which is the rotation of the

earth. The force created by the earths

rotation is called Coriolis force.


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The Coriolis force deflects air to the right in

the Northern Hemisphere.

The amount of deflection differs depending

on the latitude.

The magnitude of the force depends alsoon the speed. The faster the speed, the

greater deviation.

The speed of the Earths rotation causes

the flow to break into 3 distinct cells in each

hemisphere - Hadley cell, Ferrel cell, Polarcell.


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Hadley cell

Ferrel cell

Polar cell

Circulation Pattern

Circulation patterns are further

complicated by seasonal changes,

difference between surfaces of

continents and oceans, and other

factors.

Frictional force caused by the

topography of the Earths surface

changes the movement of air in

the atmosphere.


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Surface Analysis Chart


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Low Pressure Area Lows are frequently associated with

stronger winds and atmospheric lift.

This lift will generally produce cloud

cover, due to adiabatic cooling, once

the air becomes saturated as it rises.

It turns counter clockwise in the

northern hemisphere.

Weather associated with LPA: The rising air in a low will cool and

cloud will tend to form.

Depending on the stability of air,

large CU, CB or NS cloud will form.

Rain or heavy showers.

Turbulence

Good visibility


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High Pressure Area H

igh pressure area is a region where theatmospheric pressure is greater than the

surrounding area. In some countries, these

regions may be referred to as anti-

cyclones.

Highs are frequently associated with light

winds and subsidence. Subsidence willgenerally evaporate most cloud droplets

after less than 500 meters, due to adiabatic

heating.

Weather associated with HPA:

The subsiding air in a low is stable.

As air descends and warms, any cloud

tends to disperse.

Poor visibility due to stable atmosphere.

Fine weather but hazy.


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Col

It is a region between twoH

PAs and twoLPAs.

It is an area of almost constant pressure

with isobars bending away from the center.

Weather associated with Col:

The wind is typically light and variable.

Fog is possible (during winter) and high

temperature (in summer).

Weather generally is unpredictable.


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Wind It is the flow of air in horizontal motion due to

the difference in pressure between two joining

air masses.

On a MSL Synoptic Chart, the isobars, which

joins lines of equal pressures, indicate both

wind speed and direction.

If the isobars are close together, wind isstrong. And the further apart the isobars the

weaker the wind.


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Local windsSea Breeze (A)

It is a wind from the sea that develops over

land near coasts.

It is formed by increasing temperature

differences between the land and water

which create a pressure minimum over the

land due to its relative warmth and forces

higher pressure, cooler air from the sea to

move inland.

Land Breeze (B) It occurs exactly opposite reason to sea

breeze.

At night, the land cools more quickly than

the sea.

The result is that the flow of air is now from

the land out to the sea.

Land breeze are strongest during the early

hours of the morning.


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Katabatic wind It is a wind that blows down a

mountain slope during the night and in

the early morning when the land loses

heat by radiation.

The land then cools the air in contact

with it and on a slope the dense air

mass slides down the slope under

the influence of gravity.

The katabatic wind speed depends on:

The size and steepness of the

mountain

How cloudy the sky is

Surface friction Length of the night

Anabatic wind The opposite of katabatic wind.

This less dense air flow up the slope.


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Mountain waves

When a wind flows towards a mountain

producing a series of standing waves. They are periodic changes of

atmospheric pressure, temperature and

orthometric height in a current of air

caused by vertical displacement.

They can also be caused by the surface

wind blowing over an plateau or even byupper winds deflected over a thermal

updraft or cloud street.


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Wind Shear

Refers to the variation of wind over

either horizontal or vertical distances,the difference in wind speed and

direction over a relatively short

distance in the atmosphere.

An additional hazard of turbulence is

often associated with wind shear.

It is commonly observed nearmicroburst and downburst caused by

thunderstorms, weather fronts, areas

of locally higher low level winds

referred to as low level jets, near

mountains, radiation inversions that

occur due to clear skies and calmwinds, buildings, wind turbines, and

sailboats.


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Wake Turbulence

The turbulence that is formed behind

an aircraft as it passes through theair. This turbulence includes various

components, the most important of

which are wingtip vortices and

jetwash.

These vortices are at its greatest

strength when the aircraft generatingis heavy, clean, and slow.

Wake turbulence is especially

hazardous during the landing and

takeoff phases of flight.

Wake turbulence generation begins

at rotation and ends at touchdown.


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Atmospheric Stability

As a parcel of air rises the pressure around it

reduces. Therefore as is rises, it will expand and it

will cool. The air is said to be cooling adiabatically.

Adiabaticmeans a change in temperature not due to

heat transfer but a change in pressure around its

surroundings.

The lapse rate is the change of atmospheric

temperature with height.

Environmental Lapse Rate

Adiabatic Lapse Rate

Definitions:


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When unsaturated air cool adiabatically at

approximately 3rC/ 100 feet, this is known as

Dry Adiabatic Lapse Rate (DALR).

When saturated air in a form of water vapor

changes to liquid, it gives off latent heat, it

slows down the adiabatic cooling process.

The air cools at a slower rate, this is called

Saturated Adiabatic Lapse Rate (SALR) at

approximately 1.5rC/ 1000 feet.

Adiabatic Lapse Rate

Refers to the actual change of temperature

with altitude for the stationary atmosphere.

The ELR at a given place varies from day today and even during each day.

As an average, the ICAO defines an ISA with

a temperature lapse rate of 1.98 rC/1,000 ftfrom sea level to 11 km (36,090 ft).

Environmental Lapse Rate


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Atmospheric stability is the airs resistance to any

disturbing effect.

The ability to resist the narrowing of the spread

between air temperature and dewpoint.

Atmospheric Stability

The lapse rate determines the atmosphere's

resistance to vertical motion, or stability.

If the lapse rate equals the DALR then there is

no resistance to vertical motion.

If the lapse rate is larger, or "more stable" the

atmosphere resists vertical motion.

An atmosphere in which the lapse rate is smaller

(more negative) than the DALR is "unstable" andtends to spontaneously mix.

The only region of the atmosphere which is

generally unstable is the layer immediately

above heated ground, in which thermals form.


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Temperature Inversion

It is a deviation from the normal change of

an atmospheric property with altitude (an

increase in temperature with height).

When there is an inversion, it indicates a

very stable atmosphere.


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Types of Inversion

Radiation Inversion

Occurs after an overnight cooling of the

ground which in turn cools the lowest

layer of the atmosphere.

Subsidence Inversion

Usually occurs when different density of

air in the atmosphere subside morecausing some adiabatic warming.

When a warm layer of air overlying

colder air occurs about 4000 to 6000

feet above the earths surface,

inversion sets in.

Frontal Inversion Movement of a cold front results in cold

dense air forcing warmer air aloft.


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Clouds

A cloud is a visible mass of droplets or frozen

crystals floating in the atmosphere above the

surface of the earth.

All clouds are divided into 3 groups based on

the height of theirbase.

High Clouds

Usually forms above 20,000 feet AGL and

form only in stable air.

They are made of ice crystals and pose

no real threat of turbulence or airframe

icing.

Typical high clouds are cirrus, cirrostratus,

and cirrocumulus.


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Mid-level Clouds

Usually forms between 6,500 feet AGL and

extends up to 20,000 feet AGL.

They are composed of water, ice crystals, andsuper-cooled water droplets.

Typical middle-level clouds include altostratus

and altocumulus.

Altostratus clouds can produce turbulence and

may contain moderate icing.

Altocumulus clouds, which usually form when

altostratus clouds are breaking apart, also may

contain light turbulence and icing.

Low Clouds

Low clouds are those that form near the Earths

surface and extend up to 6,500 feet AGL.

They are made primarily of water droplets, but can

include super-cooled water droplets that induce

hazardous aircraft icing.

Typical low clouds are stratus, stratocumulus, and

nimbostratus.


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Basic cloud types


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Precipitation from clouds

Drizzle

Consist of very small water droplets.This type of precipitation is

associated with stratus clouds.

Rain Large water droplets coming from

nimbostratus cloud. Also varying

degrees from stratocumulus andaltostratus clouds.

Showers Occurs as a sudden start and

stopping of precipitation with clear

breaks in between. These fall withvarying degrees of intensity from

cumulus, cumulonimbus and

altocumulus type of clouds.

Hail Usually occurs from large towering

cumulus and cumulonimbus type of

cloud.

Snow

Occurs when star shaped icecrystals develop within a cloud

before falling. This is most

commonly seen from the stratus

group of clouds.

Virga

This doesnt reach the ground, so its

not really precipitation. The rain falls

from the base of a cloud but

evaporates before it reaches the

ground.


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Fog and Mist Fog is a form of stratus cloud at low level

with the horizontal visibility down to below1000 meters.

If the visibility is 1000 meters or more,

then it is known as mist.

Basically fog forms by the same method

as cloud. Fog types are categorized

according to how they form.

Fog is one of the most frequent causes of

low visibility at airports and as such is a

significant hazard to aviation.

Fog forms when the difference between

temperature and dew point is generally

less than 2.5rC.


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Radiation fog

is formed by the cooling of land after sunset

by thermal radiation in calm conditions with

clear sky. The cool ground produces condensation in

the nearby air by heat conduction.

Radiation fogs occur at night, and usually

do not last long after sunrise.

Advection fog

Occurs when moist air passes over a cool

surface by advection (wind) and is cooled.

Wind is required to form advection fog.

Winds of up to 15 knots allow the fog to

form and intensify; above a speed of 15

knots, the fog usually lifts and forms low

stratus clouds.

Advection fog is common in coastal areas

where sea breezes can blow the air over

cooler landmasses.


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Steam fog

Forms when cold, dry air moves over

warm water. As the water evaporates,

it rises and resembles smoke. This type of fog is common over bodies

of water during the coldest times of the

year.

Low-level turbulence and icing are

commonly associated with steam fog.

It often causes freezing fog, or sometimes hoar frost.

Dispersal of fog

Sun light to warm up the earths

surface.

An increase in wind strength.


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Thunderstorms Thunderstorm is a form of weather

characterized by the presence of lightning and thunder.

It is a cumulus cloud that has grown

into a cumulonimbus.

For a thunderstorm to develop, it

needs the following:

An unstable atmosphere

Abundant moisture to feed

the cloud.

A trigger to start the air rising.


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Thunderstorm can be defined by the trigger that

starts the air rising:

Convective storms are caused by surfaceheating over land in summer.

Frontal storms are caused by cold front

forcing warmer air upwards.

Orographic storms are started by air rising

over a mountain.

Nocturnal storms occur over the ocean atnight and are caused by cooling at the top of

a large cumulus cloud.


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Life cycle of a thunderstorm

Cumulus stage ischaracterized by warm,

strong updrafts which may

be as fast as 4000 feet per

minute. No precipitation at

this stage.

Mature stage is

characterized by both

updrafts and downdrafts,

extremely turbulent.

Lightning and rain begins

at this stage.

Dissipating stage last stageof an active thunderstorm.

Both updrafts and downdrafts

mix weakens leaving a

continuous rain until the cloud

is empty.


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Air mass and FrontsAir mass

Is a large volume of air that havecharacteristics of temperature and

water vapor content.

Air masses cover many hundreds or

thousands of square miles, and

slowly change in accordance with the

surface below them. They have continental and maritime

source regions, with different

temperature and moisture

characteristics..

Groupings: Tropical maritime form over

warm tropical waters and bring

warm, moist air.

Tropical continental

Polar maritime forms over a

polar region and brings cool,

dry air with it.

Polar continental


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Cold front

Occurs when a mass of cold, dense, and stable air

advances and replaces a body of warmer air.

Cold fronts move more rapidly than warm fronts,

progressing at a rate of 25 to 30 m.p.h.

A typical cold front moves in a manner opposite that of a

warm front; because it is so dense, it stays close to the

ground and acts like a snowplow, sliding under the

warmer air and forcing the less dense air aloft.


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Prior to the passage of a typical

cold front, cirriform or towering

cumulus clouds are present, andcumulonimbus clouds are possible.

Rain showers and haze are

possible due to the rapid

development of clouds.

The wind from the south-southwest

helps to replace the warmtemperatures with the relative

colder air.

A high dewpoint and falling

barometric pressure are indicative

of imminent cold front passage.

As the cold front passes, towering

cumulus or cumulonimbus clouds

continue to dominate the sky. Depending on the intensity of the

cold front, heavy rain showers form

and might be accompanied by

lightning, thunder, and/or hail.

More severe cold fronts can also

produce tornadoes. During cold front passage, the

visibility will be poor, with winds

variable and gusty, and the

temperature and dewpoint drop

rapidly.

Temperature will fall and barometric

pressure begins to gradually

increase.

Before passage: After passage:


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Warm front

Occurs when a warm mass of air advances and

replaces a body of colder air.

Warm fronts move slowly, typically 10 to 25 miles per

hour (m.p.h.).

The slope of the advancing front slides over the top of

the cooler air and gradually pushes it out of the area.

Warm fronts contain warm air that often has very high

humidity. As the warm air is lifted, the temperature drops and

condensation occurs.


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Prior to the passage of a warm

front, cirrus, cirrostratus, altostratus,

nimbostratus are present. Thenstratus and fog.

Heavy continuous rain because of

rising of stable air forming stratiform

clouds or NS.

Wind from the south-southeast.

Cool temperature and steadilyfalling barometric pressure are

indicative of warm front passage.

Poor visibility.

Clouds starts to clear up.

Some light rain or showers.

Temperature starts to warm upwhile pressure slightly rise.

Before passage: After passage:


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Tropical Cyclone Cyclones are intense low pressure

systems that develop in tropical oceans. The main difference between cyclones

and other depressions is the destructive

winds which can reach speeds of up to

150 knots.

The main characteristics are:

They form between about 5 and 15latitude N.

They form over water whose

temperature is about 28C or warmer.

The lowest surface pressure is in the

eye. The strongest winds are around the

eye.


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Cyclone formation and track


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Meteorological ServicesAerodrome Forecasts (TAF)

A Terminal Aerodrome Forecast (TAF) refers to the forecast conditions

within a 5 NM radius of the center of an aerodrome or runway complex.

New format (TAF)


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Weather codes and translation


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JANDAKOT (YPJT)

TAF AMD YPJT 171043Z 1712/1806

25010KT 9999 LIGHT SHOWERS OF RAIN FEW015 BKN030

FM171700 21005KT 9999 SCT015FM180200 21013KT 9999 SCT030

PROB30 1719/1724 0300 FOG

RMK

T 19 18 16 15 Q 1015 1015 1015 1016

PERTH (YPPH)

TAF AMD YPPH 171040Z 1712/181825010KT 9999 LIGHT SHOWERS OF RAIN FEW015 BKN030

FM171700 21005KT 9999 SCT015

FM180200 21013KT 9999 SCT030

PROB30 1719/1724 0300 FOG

RMK

T 21 18 16 15 Q 1014 1014 1014 1015

HONG KONG (

VHHH)TAFVHHH 171100Z 1712/1818 15010KT 8000 FEW025 TX27/1807Z

TN19/1723Z BECMG 1715/1717 VRB05KT TEMPO 1718/1806 3000 HZ BR

BECMG 1802/1804 29010KT BECMG 1809/1811 12005KT

(TAF) samples


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Aerodrome Weather Reports (METAR)

A Aerodrome Weather Report (METAR) is a report of an actual observation

of weather conditions.

HONG KONG (VHHH)

VHHH 171100Z 1712/1818 15010KT 8000 FEW025 TX27/1807Z TN19/1723Z

BECMG 1715/1717 VRB05KT TEMPO 1718/1806 3000 HZ BR

BECMG 1802/1804 29010KT BECMG 1809/1811 12005KT

VHHH 171600Z 11006KT 060V160 9999 FEW015 23/18 Q1013 NOSIG

SINGAPORE (WSSS)

WSSS 171100Z 1712/1818 VRB05KT 9999 FEW018CB SCT020

TEMPO 1802/1806 4000 THUNDERSTORMS WITH RAIN SCT015CBBKN018

WSSS 171630Z VRB01KT 9999 FEW018 BKN300 27/25 Q1010 NOSIG

MANILA (RPLL)

RPLL 171100Z 1712/1812 12008KT 9999 SCT025 SCT100 TX31/1806Z TN24/1721Z

TEMPO 1712/1718 10005KT 8000 -RA SCT023 BKN090RPLL 171600Z 12006KT 8000 SCT023 BKN100 26/25 Q1012 NOSIG RMK A2989

LAPU-LAPU (RPVM)

RPVM 171100Z 1712/1812 04008KT 9999 FEW020 SCT100 BKN250

TEMPO 1712/1718 02006KT 9000 FEW018CBFEW020 BKN090

RPVM 171600Z 34004KT 9999 FEW020 BKN300 25/23 Q1011 A2985


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ATIS YPPH K 171616

+ APCH

:RWY: 21 AND 24 FOR ARR.

RWY 21 FOR DEP

OPR INFO: TWY LIMA 2 AND

CHARLIE 3, NOT AVBL DUE WIP.

DEP FREQ 118.7

WND: 230/8

VIS: GREATER THAN 10 KM

CLD: SCT035TMP: 19

QNH: 1015

Automatic Terminal Information Service (ATIS)

Is a continuous broadcast of recorded

non-control information in busier terminalareas.

ATIS broadcasts contain essential

information, such as weather information,

which runways are active, available

approaches, and any other information

required by the pilots, such as importantNOTAMs.

Pilots usually listen to an available ATIS

broadcast before contacting the local

control unit, in order to reduce the

controllers' workload and relieve

frequency congestion. The recording is updated when there is a

significant change in the information, like

a change in the active runway. It is given

a letter designation (e.g. bravo), from the

phonetic alphabet.

ATIS YMML W 171616

RWY 16 FOR ARRS.

RWY 27 FOR DEPSWND: 200/6

VIS: GREATER THAN 10 KM

CLD: BKN022

TMP: 13

QNH: 1018


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- END -


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Example When the bicyclist runs over the nail, the air, having a higher pressure than

the outside air, will rush out. The air does work against the atmosphere asit rushes out from the tire. In doing this work of displacing the outside air,the air from the tire must use some energy. That energy comes from thekinetic molecular energy. The kinetic energy of the molecules from the tireslows and the temperature falls.

No heat has been added or removed from the system yet the expanding aircools.This process is called Adiabatic Cooling. It is also called ExpansionCooling.

This process is reversible.

If we took a pump to compress the air, as we would if we were filling the tire,

then the energy used to compress the air is used to increase the kineticenergy of the molecules. Compression warms the air.This process is called AdiabaticWarming.


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Example 1

if we raise a parcel of air from ground level to100 meters in height, the temperature willdecrease by 1rC. The parcel cools at a rate of1rC per 100 m or 10rC per km.

The parcel expanded and did work on itsenvironment!

Now, bring the parcel back down to thesurface. The environment did work on theparcel.

This is an adiabatic process and is reversible.


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Example 2:

If we use a moist parcel of air (RH = 100%)

The rising air cooled and produced condensation. Thecondensation released latent heat so the rising parcel

does not cool as rapidly with height as a dry parcel. Parcel cools only 0.6rC per 100 m (on average).

Moist adiabatic lapse rate = 0.6rC per 100 m.Remember -- This is an average lapse rate. The actualone varies!!!

If the moisture falls out of the parcel as rain, theprocess is not reversible.

Reversible only if no moisture has been removed!


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If we (somehow) lift the parcel: It will cool at the dry adiabatic lapse rate. The parcel

will find itself cooler than the environmental (sounding) temperature. At the same

pressure, a cooler parcel will be denser than the environment. Being denser, the

parcel will descend back to where it came from.

STABLE!

If we (somehow) lift the parcel: It will cool at the dry adiabatic lapse rate.


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The parcel will find itself warmer than the environmental (sounding) temperature.

At the same pressure, a warmer parcel will be less dense than the environment.

Being less dense, the parcel will ascend and move farther from where it came from.

UNSTABLE!



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The parcel will find itself at the same temperature than the environmental (sounding)

temperature.

Being the same density, the parcel will not be accelerated in any direction and will remain

where it is.

NEUTRAL STABILITY! -- Dry Neutral, orConditional Instability

Wh t t i th i i i ?


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What triggers the rising air?

Convection


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Frontal Lifting


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Converging surface winds


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Vertical Cross Section View


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Stretching Process

Vertical

stretching (like

by a strong

updraft) also

increases

rotation


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Splitting Process

Right Moving Supercell


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Right-Moving Supercell

Processes


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Storm Tilt Vertical wind shear

and buoyancygradients across thecloud act to tilt theconvective tower inthe downsheardirection. For agiven amount ofshear, a stronger,updraft will not tilt as

much as a weakerupdraft simplybecause its verticalmomentum isstronger.

Right Moving Supercell


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Right-Moving Supercell

Processes


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Additional Effect


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Temperature Inversions

What is an inversion?

An inversion is a stable zone in the atmosphere.

Inversions that are weak may only last a day

while strong inversions can stay around formultiple days until the weather changes. During

a strong inversion, pollution is trapped under this

cap, preventing exhaust like carbon monoxide

from vehicles and wood stoves to mix or rise upin the atmosphere.


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Temperature Inversions


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Change of state

Evaporation is the process by which

molecules in a liquid state (e.g. water)

spontaneously becomes a gas (e.g. water

vapor), without being heated to the boilingpoint. It is the opposite of condensation.

Generally, this manifests as the gradual

disappearance of the liquid, when exposedto a significant volume of gas.


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Change of state

Condensation is the change in matter of

a substance to a denser phase, such as a

gas (or vapor) to a liquid.[1] Condensation

commonly occurs when a vapor is cooledto a liquid, but can also occur if a vapor is

compressed (i.e., pressure on it increased)

into a liquid, or undergoes a combinationof cooling and compression.


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Change of state

Sublimation of an element or compound is the

change from a solid directly to a gas with no

intermediate liquid stage

Deposition is a process in which gas transforms into

solid. The reverse of deposition is sublimation.

One example of deposition is the process by

which, in sub-freezing air, water vaporchanges

directly to ice without first becoming a liquid.

This is how snow forms in clouds, as well as

frost and hoar frost on the ground.


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MOISTURE

Humidity is the amount ofwater vaporin air. Absolutehumidity, relative humidity, and specific humidity aredifferent ways to express the water content in a parcel ofair. Relative humidity is the most frequently used of

these expressions because of its importance in weatherforecasting.

Relative Humidity is a term used to describe theamount of water vapor that exists in a gaseous mixtureof air and water, expressed as a percentage of the

maximum amount of water vapor that could be present ifthe vapor were at its saturation conditions


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CALCULATING CLOUD BASES

Dewpoint- dew point of a given parcel ofairis thetemperature to which the parcel must be cooled, atconstant barometric pressure, forwater vaportocondense into water, called dew.

Cloud bases Unsaturated air 5.4 F/ 1000ft.

Dewpoint Temperature cools 1F/1000ft

4.5F/1000ft Converge

Temperature (F) Dewpoint (F) x 1000ft4.5F


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Meteorology 2